Abstract

Late Proterozoic glaciation between 800 and 600 Ma represents one of the most puzzling climatic events in Earth history. Over the past three decades, increasing evidence has emerged in several continents for the occurrence of Late Proterozoic ice-sheets near sea-level in low palaeolatitudes. Although some early palaeomagnetic data are equivocal or contentious, palaeomagnetic studies since 1980 consistently have indicated glacial deposition in low palaeolatitudes (0–12). Positive fold tests on soft-sediment slump folds in fine-grained sandstone from the Marinoan glacial succession in South Australia confirm the primary nature of the stable remanence and low palaeomagnetic inclination (< 10) of these rocks. Coeval glaciation in high palaeolatitudes has not been demonstrated; indeed, the North China block occupied high palaeolatitudes (57–62) in Late Proterozoic time but affords no evidence of glaciation. Structures interpreted as periglacial sandwedges of seasonal contraction–expansion origin, clearly displayed with other periglacial features in a fossil permafrost horizon in South Australia, imply mean annual air temperatures as low as – 12 to – 20 C or lower in coastal terrain near sea-level and strongly seasonal climates (seasonal temperature range as great as ∼40 C or more). Time-series analysis of tidal–climatic data from coeval rocks in South Australia provides independent evidence of a powerful annual signal. Furthermore, grounded ice-sheets and glacial pavements formed near sea-level in Australia and other continents during the Late Proterozoic. Palaeomagnetic and palaeoclimatic data, provided most clearly by recent studies of Late Proterozoic rocks in Australia, thus present the enigma of frigid, strongly seasonal climates, with permafrost and grounded ice-sheets near sea-level, in low palaeolatitudes.